Multifunctional keplerate-type polyoxometalate-organic polymer composite films for interface engineering in perovskite photodetectors

Interfacial contact and morphology control are vital to obtain high performance planar-structure perovskite photodetcetors. The substrates where the perovskite film covered are expected to direct the growth of perovskite crystal and possess suitable energy level to accept the photoelecctrons effectively. Here we firstly modify the substrate via interface engineering by using W72V30-polyethyleneimine (PEI) multifunctional interlayer. With the incorporation of W72V30, the optimized morphology perovskite films are formed by controlling the crystallization kinetics of perovskite with fewer trap states. Simultaneously, the transfer of photoelectrons become more efficient due to the better energy level alignment between W72V30 and perovskite. Besides, rich animo group of the exposed PEI provide the interlayer with wetting property, resulting in a better interfacial contact between substrate and perovskite films. As a result, the photodetectors possess high-quality perovskite film and fewer electron recombinations at the surfaces and interfaces. The photodetectors reveal that the photocurrent increase from 4.5 μA to 9.1 μA, the on/off ratio is 3.99 × 103 and the photoresponsivity is 6.02 mA W−1 under simulated AM 1.5 illumination. The study on W72V30-PEI composite film provides not only a promising multifunctional material for interface engineering but also a facile method to reduce trap states on perovskite surface.